Determination of purines in soybean milk by capillary electrophoresis in comparison with high performance liquid chromatography

A simple capillary electrophoresis (CE) method with UV detection was developed for the determination of four purines including adenine, guanine, hypoxanthine and xanthine in soybean milk. Acid hydrolysis was used as sample preparation approach, and the effects of several important factors were investigated. Separation of the four purines was achieved in 5 min using 10 mmol L-1 sodium borate and a voltage of 25 kV. Under the optimal conditions, the linear range was from 0.5 to 100 mu g mL(-1) and the detection limits were from 0.05 to 0.09 mu g mL(-1). The developed method showed good repeatability for the quantification of the four investigated purines with intra-and inter-day RSD of less than 3.0% and 4.5%, respectively. The optimized acid hydrolysis followed by CE method was successfully applied to determine the purines in different kinds of soybean milk samples. Furthermore, a comparison of the results obtained by the proposed CE method was made with those of high-performance liquid chromatography (HPLC). The performance of CE was comparable, and the quantitative results were in good agreement with those by HPLC, while the CE method had the advantages of much shorter analysis time and lower cost than HPLC.